Asda had argued that because different departments ran the shops and the distribution centres, and as there were different methods for setting pay, that no comparison was possible.

In the October judgment the employment tribunal dismissed Asda’s claims and agreed with the claimants that both sets of workers were employed by Asda and that the pay for all workers was controlled by Asda’s executive board, and overseen by their parent company Wal-Mart.

Asda appealed the tribunal’s October decision on ten different grounds. All were unsuccessful.

The Honourable Mr Justice Kerr concluded today that the employment tribunal had been correct in saying that shop workers could compare to the distribution workers:

“I find no lack of rationality or perversity in the judge’s reasoning […] the judge’s overall conclusion that the terms were common in the statutory sense is not impeachable.”

“Asda continues to appeal every point available to them, rather than focusing on paying men in the distribution centres and women in the stores equally, but judges at every level have been adamant that the claims can continue.

“After yet another defeat, we hope that Asda take this opportunity to reflect on the merits of the claims, and concentrate on why they pay men more than women for jobs of equal value, rather than trying to stop the claims going ahead at all.”

Tim Roache, GMB General Secretary, said:

"GMB look forward to Asda management sitting down and finding a sensible negotiated solution to recognising that our female members in stores should be paid and valued as equal to the men.

"Instead of wasting money on litigation, we ask Asda to be a market leader in solving this wide ranging industry problem."

Asda have indicated that they will seek permission to appeal the decision again.

If the shop workers are ultimately successful in their claims Asda are likely to have to review the pay of tens of thousands of staff who may have been paid unlawfully.